Hi,
Thanks to all of you that responded to my question about consumer-level insert earphones for use in neurophysiological experiments. I was recently able to get my hands on two phones from Shure, the E3C and E4C. The specs for these phones can be found here: http://www.shure.com/PersonalAudio/Products/Earphones/ESeries/us_pa_E4c_content
I have not yet found any consumer-level (not professional) Etymotic phones to test.
The nice thing about the Shure phones is that a short tube can couple the phones directly to a piece that fits into the ear canal of our animals (for design, see Figure 4 in Chan et al (1993) An insert earphone system for delivery of spectrally shaped signals for physiological studies, JASA 93:1496-1501). The design allows for in-situ calibration of the system. For the tests below, we used a B&K Type 4182 probe microphone and the earphone system described above was terminated with a 0.2cc coupler.
The attached JPG figure shows calibrations into the system described above for 3 phones:
1) Shure E4C with a 442mV (peak) signal
2) Shure E3C with a 222mV (peak) signal. Note this is 6dB down from the E4C. The E3C was saturating the mic at low freqs, so 6dB should be added to the E3C calibration shown in the fig.
3) Tucker-Davis (TDT) EC1 electrostatic with a 9.9V (peak) signal. We are currently using these for our studies.
The Shure E4C produced a really nice response through ~17kHz. The E3C has a strange dip at ~12kHz. The EC1 has a large frequency range, but generally can't produce much more than ~90-95 dB SPL (after application of an FIR correction/flattening filter). The E4C gives 10-15 dB more dynamic range, at least through 17kHz; these phones can produce ~105dB SPL (+-2dB, after flattening with FIR correction filter). This is as good as the Etymotic ER-2 tubephones, but at 1/3 the cost. The Shure phones can also be fitted directly with the foam eartips. The Shure E4C phones are a viable option for neurophysiological studies in animals with low-frequency (<~17kHz) hearing (chinchilla, guinea pig, hamster, gerbil, etc).
Daniel J. Tollin, PhD
Assistant Professor
University of Colorado Health Sciences Center
Department of Physiology and Biophysics/Mail Stop 8307
Research Complex 1-N, Rm 7120
12800 East 19th Ave
PO Box 6511
Aurora, CO 80045
Tel: 303-724-0625
Fax: 303-724-4501